BMR Calculator

Basal Metabolic Rate is the number of calories your body burns to keep you alive at complete rest. It covers breathing, circulation, cell repair, and keeping your organs running, before any movement or digestion adds to the total. For most people, BMR accounts for the largest share of daily energy use, often around 60% to 70% of the total.

This calculator uses the Mifflin-St Jeor equation, which research finds more accurate for modern populations than older formulas. The male version is $BMR = 10w + 6.25h - 5a + 5$, where $w$ is weight in kilograms, $h$ is height in centimeters, and $a$ is age in years. The female version ends in $-161$ instead.

Knowing your BMR gives you a baseline. Everything you do on top of resting, from walking to training, adds calories above this floor. That makes it the starting point for any calorie plan, whether you want to lose, maintain, or gain. Because the equation only needs your age, sex, height, and weight, you can recompute it whenever those numbers change and keep your plan grounded in current figures rather than old estimates.

Your BMR only describes rest, so the calculator multiplies it by an activity factor to estimate Total Daily Energy Expenditure, or TDEE. This is the figure that matters when you plan meals, because it reflects how much you actually burn across a normal day.

The tool offers five activity levels. Sedentary multiplies BMR by 1.2, lightly active by 1.375, moderately active by 1.55, very active by 1.725, and extra active by 1.9. Pick the level that matches a typical week, not your best week.

For example, a person with a BMR of 1,600 who is moderately active has a TDEE near 2,480 calories. Eating around that amount tends to hold weight steady over time. The calculator shows the figure for every activity level at once, so you can see how training more or sitting more changes your needs without re-entering your details. That side-by-side view also helps if your routine shifts week to week, since you can read off the level that matches your current pattern instead of recalculating each time.

Once you know your TDEE, adjusting it sets a clear calorie target. Eating fewer calories than you burn creates a deficit and leads to weight loss, while eating more creates a surplus for weight gain. The calculator builds these targets for you.

A daily change of 500 calories is a common, sustainable step. Roughly 7,700 calories equal one kilogram of body fat, so a 500 calorie deficit predicts about 0.5 kg of loss per week. The tool subtracts 500 from your TDEE for a loss target and adds 500 for a gain target.

These numbers are estimates, not guarantees. Metabolism, water shifts, and changes in activity all affect real results, so two people following the same target can progress at different rates. Treat the target as a starting plan, check your progress after a few weeks, and adjust if the scale is not moving the way the math predicts. Small, steady changes tend to hold up far better than aggressive cuts that are hard to sustain past the first week or two.

Several factors push BMR up or down, which is why two people of the same weight can have different needs. Muscle is more metabolically active than fat, so a leaner, more muscular body burns more at rest. Building muscle through strength training raises your floor over time.

Age plays a role too. BMR tends to fall as you get older, partly because muscle mass declines, which is why the equation subtracts more for higher ages. Sex matters as well, since men typically carry more muscle and so have a higher baseline than women of the same size.

Height and weight feed directly into the formula, so a larger body burns more simply by having more tissue to maintain. Crash dieting can lower BMR as the body adapts to less fuel, which is one reason very aggressive diets often stall. Understanding these drivers helps you read your result and plan changes that actually shift your numbers rather than fighting against your own physiology. It also explains why two people of identical weight can need noticeably different amounts of food each day.

BMR works best as one part of a wider picture. It tells you how many calories you need, but it says nothing about whether your weight sits in a healthy range or how your body is composed. Pairing it with other measurements gives a fuller view.

The BMI Calculator shows whether your weight relates well to your height, which helps you decide whether a loss or gain target makes sense in the first place. The Ideal Weight Calculator suggests a target weight for your frame, giving your calorie plan a destination.

Age feeds directly into the BMR formula, so an accurate figure matters more than people expect. The Age Calculator confirms your exact age if you are unsure, which keeps the resting estimate honest. Together these tools let you move from a single resting number to a complete, grounded plan for managing your weight with realistic, repeatable targets. Used together rather than in isolation, they turn a quick estimate into a routine you can actually follow and revisit as your body changes.